This project and is designed to accomplish the following aims: (1) To determine the extent to which AIDS-related stressors (bereavement and HIV infection) lead to changes in mental health, substance use, and sexual behavior; (2) To construct and compare theoretically based causal models of the process leading from the experience of AIDS-related stressors to changes in psychosocial functioning as mediated by personal characteristics and factors in the social environment; (3) To evaluate the influence of health-related behaviors (substance use, sexual behavior, coping activities), psychological distress, and social support on disease progression among HIV infected individuals. In addition to this ongoing work, the applicant is beginning two new studies. The first is a study of young gay men, age 18 to 23, designed to (1) estimate levels of sexual behavior in this population, (2) evaluate the process by which these young gay men acquire attitudes towards AIDS and HIV testing, and (3) study the extent of their exposure to AIDS-related stressors and coping efforts associated with such exposure. The second study is an intensive follow-up of individuals with AIDS in order to determine psychological, social, and behavior factors associated with illness progressions.